Hydrocarbon conversion process



May 16, '1944.

F. E. FREY -HYDROCABO CONVERSION PROCESS Filed Oct. '7, 1940 .mi moho:@n

esses in which there is a Patented May 16,. i944 HYIDROCARBON CONVERSIONPROCESS )Frederick E. Frey, Bartlesville, 0kla., assignor to PhillipsPetroleum Company, a corporation of helaware Application October 7,1940, Serial No. 360,163 7 Claims. (Cl. Zim- $83.11)

This invention relates to the conversion of light hydrocarbons to formvaluable motor fuel stocks. More particularly it relates to acooperative combination of process steps for producing predominantlyaliphatic hydrocarbons in the motor fuel boiling range. It relates moreparticularly to converting mixtures of hydrocarbons containinghydrocarbons having at least two and not more n than live carbon atomsper molecule.

' Many processes have been proposed for converting normally gaseoushydrocarbons into hydrocarbons having higher molecular weights, such asmotor fuels and lubricants. Some of these processes are dependent uponthe presence of large proportions of oleflns in the charge stock, as inwell known thermal or catalytic polymerization processes for producingmotor fuel from renery gases containing unsaturated components fromcracking stills. vvStill other processes are adapted to produce motorfuel vfrom normally gaseous parains, such as unitary thermal conversionprocesses, multistage processes employing a dehydrogenation step as arst part of the process, followed by a polymerization of the light olensso produced, or by thermal conversion procconcomitant polymerizationofgaseous hydrocarbons and reversion of light liquid hydrocarbons. Stillother processes have been proposed` wherein a paraillnic hydrocarbonstream and an olelnic hydrocarbon stream are charged to a system, andthe parafns and olens are caused 'to interreact, or as it is generallystated, the parafns are alkylated by the olens to form paraiiins havinghigher nmolecular weights.

Although both thermal and catalytic olefinpolymerization processes canbe operated to produce, from normally gaseous oleins, liquidhydrocarbons in the motor fuel boiling range, such as a gasoline stock,I have found that the thermal processes produce a composite motor fuelproduct having generally a 'higher Yvolatility than the composite-motor-fuel product produced by catalytic polymerization from a similar chargestock. This is especially true when the thermal con- Version process isoperated at a high superatmospheric pressure to produce predominantlyaliphatic hydrocarbons in the gasoline boiling range. While in manyinstances this is an advantage, it is a disadvantage where large volumesof natural gasoline are likewise available .and it is desired to producea composite gasoline containing natural gasoline and such polymergasoline.

I have now found that, when the eluent of`a high pressure thermalconversion process which includes the treatment of normally gaseoushydrocarbons, or la selected portion of such eluent containing bothnormally gaseous and normally liquid hydrocarbons, is subjected totreatment at moderate temperatures and pressures by intimate admixturewith concentrated sulfuric acid, 'a Very desirable motor fuel stock canbe produced which has a.moderateorl1ow, volatility and which has a goodantiknock rating.

Furthermore, in so treating such a hydrocarbon mixture, in a mannersuchv as will be more fully hereinafter described, I have found thatthere is an appreciable decrease in the unsaturate content of the totalmotor fuel boiling range hydrocarbon product without an attendant largeloss of hydrocarbon material from this boiling range, such as has beenexperienced in the past Ifrom treatment of an unsaturate-containingmotor fuel or motor fuel stock with sulfuric acid to remove sulfur compounds and gum and color-forming bodies, and the like. While the exactreason for this is not known, I believe that, at least in part, it isdue to the fact that high pressure thermal convension of lighthydrocarbons produces substantial proportions of low boiling, normallyliquidrisoparailn hydrocarbons, and that the low boiling olens presentin the thermal conversion eluent which is treated in the second part ofmy process unite with these low-boiling isoparains to form other paranhydrocarbons which are higher boiling but still within the motor fuelboiling range and which have good antiknock ratings. This effect isprobably especially predominant in those modifications of my processwhich include,

as the thermal conversion step, a thermal alkylation step such as I havedescribed in my U. S. Patent 2,002,394 and 2,104,296, and in mycopending application Serial No. 82,954, now Patent 2,270,700 grantedJanuary 20, 1942, and in the patent of Frey and Hepp, 2,209,450,together with copending divisions thereof, and it is a specicmodification of my invention to subject normally gaseous parafn and olenhydrocarbons to con-- ditions suitable for thermal alkylation, andsubsequently to treat at least a portion of the emuent, comprising bothnormally gaseous and liquid hydrocarbons, with concentrated sulfuricacid, as

will be described.

It is to be understood, of course, that normally liquid hydrocarbonproducts produced by high pressure thermal conversion and in the motorfuel boiling range, or even in the lower part of this range, will not beentirely aliphatic, and that a-relatively small amount of thehydrocarbons will be ofaucyclic nature and will combine with olenhydrocarbons to produce alkyl derivatives. Such minor compounds andreactions do not detract in any appreciable manner from the eiiciency ofmy process, andwhile such reactions may in fact contribute to the totaldesirable result, it is not believed that these are the principal orpredominant reactions. In any event, it will be noted in the following,tion of one modification of my invention, that the ,entire hydrocarbonmaterial'charged to the sulmore detailed descrip-v furic acidreaction,'or alkylation, step is derived y from thel preceding highpressure thermal conversion step, and this is a feature of my invention.

It is an object of my invention to produce normally liquid hydrocarbonsin the motor fuel boiling range from hydrocarbon mixtures containingnormally gaseous hydrocarbons.

It is a further object of this invention to sub-- mit normally gaseoushydrocarbons to thermal conversion under high pressures to producenormally liquid hydrocarbons having a relatively high volatility, andsubsequently in a second process step to produce from the eiliuent ofsuch a conversion a hydrocarbon motor fuel stock having a lowervolatility.

Other objects, and advantages, of my invention will become apparent fromthe accompanying disclosure and discussion.

A modification of my invention will now be described in connection withthe accompanying drawing, which forms a 'part of this specification andwhich shows diagrammatically, one arrangement of apparatus forpracticing my invention for the production of motor fuel from gaseoushydrocarbons.A

A normally gaseous mixture of hydrocarbons having not less than two normore than five carbon atoms per molecule, and which may be entirelyparaflinic such as the lighter portions of raw natural gasoline, orwhich may contain unsaturates as well, especially oleiins, such as a ca-C4 fraction from refinery vapors, is introduced to the system through apipe I and valve II to a pump I2. 'I'his stream will preferably be inliquid phase, so as to be more easily handled. The pump I2 increases thepressure on the stream to one suitable for a subsequent thermalconversion, which will generally be between 500 and 10,000 pounds persquare inch, more preferably between 1,000 and 5,000 pounds. The streamthen passes to a heating and reacting zone I3, which will be located inany suitable furnace, or similar apparatus, I4, wherein the hydrocarbonsare heated to a conversion temperature between '750 and 1200 F., andmaintained at aA conversion temperature and pressure for a time suicientto form an optimum yield of normally liquid, preduced through pipe andvalve dominantly aliphatic hydrocarbons in the motor` fuel boilingrange. The efiiuent of thev zone i3 passes through a cooler I5, andthrough pipe I6 and valve I1 to the separating means, represented by thefractionator 20 provided with a heating coil 2l at the bottom and acooling coil 22 at the top. If it is desired to treat all of theeffluent hydrocarbon stream in the subsequent acid alkylation step, thestream may be passed from pipe I6 through pipe 24 and valve 25 to thepump and mixing apparatus 26, for the treatment to be subsequentlydiscussed. Generally, however, it will be more desirable to remove rstsome of the heavier material and/ or some of the lighter gases, as willbe more fully hereinafter discussed.

The conversion which takes place in the heating and reacting zone I3 maybe any one of the several known .methods for the thermal, noncatalyticconversion of normally gaseous hydrocarbons to predominantly aliphaticnormally liqquid hydrocarbons. If the charge stock is substantiallyentirely paraiiinic, the heating part of zone I3r should be at atemperature of over 1000 F. to form a sunlcient amount of unsaturatesfor subsequent reaction, which may take place at a somewhatY lowertemperature. If `the charge stock includes refinery vapors with asubstantial content of unsaturates,` the heating part of the zone 41 toseparating means such as the fractionator should beat a considerablylower temperature m that the mixture is heated only to a temperaturesuilicient to initiate a subsequent polymerization reaction involvingthe unsaturates, i

As a modification which is especially applicable when two separatecharge stocks are available, one substantially entirely paraflnic andthe other containing an appreciable amount of unsaturates, the thermalconversion may be one of alkylation such as disclosed in my U. S.patents, 2,002,394 or 2,104,296, or my copending application Serial No.82,954, now Patent 2,270,700. In such a modication theunsaturate-containing stream of hydrocarbons, such as a mixture havingoleflns of two to five carbon atoms per molecule is intro- 3I and ispassed at a suitable elevated pressure, in the range previouslydiscussed, by pump 32 to manifold 33 and through a plurality of pipes,such as pipes 34, 35, and 36 supplied with valves 31, 38, and 39respectively, to the reaction zone I3 wherein a reaction takes placeinvolving a union of olen and paraffin hydrocarbons, forming a liquidproduct predominantly aliphatic and parafllnic, but which will of coursecontain some unsaturated hydrocarbons. It is, of course, understood thatthis showing is only diagrammatic, and other process arrangements,previously disclosed and discussed, may be used. p

As another modificatiomthe reaction zone I3 may be utilized for socalled gas reversion, wherein motor fuel range hydrocarbons having anundesirably low octane number may be reformed in the presence of lighterhydrocarbons. In such a modification, the charge stock entering throughpipe I0 will contain such liquid hydrooarbons. i

It is generally preferable to separate the heavier material formed,which may include the heavier portion of the motor fuel boiling rangehydrocarbons, and also the lighter material formed, such as hydrogen,methane, and ethane, from the effluent of the thermal conversion, and topass only the intermediateportion of the eiiluent, such as hydrocarbonshaving atoms per molecule, more preferably three to six or eight'carbonatoms per molecule, to the subsequent acid alkylation step. The heaviermaterial may be separated in the means 20 and is removed through pipe44, and may be removed from the system through valve 45. If theseparating means 20 is so operated that this stream contains anappreciable portion of hydrocarbons iny the motor fuel boiling range,the stream may be passed from pipe 44 through pipe 46 and valve 50provided with a heating coil 5I at the bottom and cooling coil 52 at thetop which can provide liquid reux. The material too heavy for use isremoved through pipe 53 and valve 54, and hydrocarbons in the motor fuelrange are removed through pipe 55 and valve 56, it being understood.that suitable conventional cooling and condensing equipment is includedto make the stream passing through valve 56 a liquid if such is desired.

Hydrocarbons in lower boiling part of the gasoline range, along withlighter hydrocarbons, are removed from the means 26 through pipe 61 andvalve 58, and may be passed through valve 59 to separating means such asthe fractionating co1- umn 60, provided with a heating coil 6| atthebottomand cooling coil 62 at the top. Hydrocarbons having at least threecarbon atoms per molecule are passed from lfractionator through v pipe63 and valve 64 to pipe'24, and lighter matethree to twelve carbon rialis removed from the system through pipe 85 and valve 66. l

In case only lighter material is to be removed from the efuent of zoneIt, the eilluent stream may be passed from pipe I6 through pipe 8l andvalve 68 to pipe 5l and on to fractionator 80. In case only heaviermaterial is to be removed from the eiiluent of zone I3, the streampassing from fractionator 2li through pipe 51 and valve 58 may be passedfrom pipe 51 through pipe 10 and valve il to pipe 2H, as will beappreciated. In following any alternative procedure, it is .of courseunderstood that unused apparatus is to be isolated or not included, bysuitable use of valves shown, as is obvious.

The hydrocarbon stream flowing through pipe 2t to pump 2S will comprisehydrocarbons having at least three and not more than twelve carbon atomsper molecule, and may or may not contain lighter and/or heavier materialas has been discussed, and is treated by being intimately admixed with asuitable quantity of concentrated sulfuric acid. The sulfuric acid isadded through duced by the thermal conversion. This may be done, and atthe same time the heavier'hydrocarbons removed from this stream, bypassing it from pipe 93 through pipe 95 and valve 96 to pipe and on intofractionator 56, or the stream may be added directly to the stream inpipe 55 -by passing from pipe 95 through pipe 91 and valve 98. Undercertain conditions of operation, lof course, the hydrocarbons passingfrom fractionator 99 through pipes 93 and 95 will be the only materialtreated in fractionator 5t.

Any low boiling material present in the eiiluent ofthe acid alkylation,and especially methane and hydrogen, may be removed from the top offractionator w, and lfrom the system, through pipe |00 and valve itl.All of the low boiling material which is not desired for inclusion inmotor fuel may be removed in this manner, but

pipe 'i5 and valve it to pipe 2t directly ahead of pump 2t, and becomesintimately admixed with the hydrocarbon stream, which is preferably inthe liquid phase. The intimate mixture, or emulsion, passes through pipe1l to the alkylator ld. and from the alkylator 18 through pipe 'I9 andvalve 8@ to the separating means 8|. 'I'he alkylator 7S may comprise along tube coil through which the stream passes with considerableturbulence, from which the heat of reaction may be readily extracted andwhich may be provided with baffles, mixers, to insure an adequateprolonged intimate admixture of the sulfuric acid and the hydrocarbonmaterial. Lightolens having at least three carbon atoms per molecule, orpolymers of such light olens such as triisobutylene, ortetraisobutylene, and/or light isoparailins such as isobutane,isopentane and the like, may be added to pipe 24l and tothis second partof the process through pipe 'l2 and valve 13, when desired.

In separating means 8| a separation is effected between 4the sulfuricacid and the hydrocarbon i material, and the sulfuric acid is removedthrough pipe 82, and may be discharged from the system through valve 33.Any part, or all, of this sulfuric acid stream may be recirculatedthroughpipe '86| and valve'85 to pipe l, and generally a portion of thestream will be so circulated, the remainder being withdrawn throughvalve 83 for purification and reclamation before being reintroduced tothe system through pipe l5. Ihe separating means 8| may also includemeans for separating and/or neutralizing the free acid, acidic products.and

esters, etc., which may be present in the hydrocarbon fraction, whichIis removed from separating means 8| through pipe B and valve 8l toa/separating system represented by fractionator Such neutralization andseparation will involve additional apparatus. not shown in detail. whichmay be understood to be included as a part of the separating means 8 l.

Ihe hydrocarbon eiliuent from the alkylator 'It is separated infractionator 90 into a normally gaseous fraction and a normally liquidfraction, the fractionation being aided by heating coil 9| and coolingcoil 92. The normally liquid hydrocarbon fraction is removed throughpipe 93, and may he discharged from-the system through valve tt. Anypart, or all, of this stream may be dlverted from pipe 93 through pipe95 to be blended, as desired, with normally liquid hydrocarbonsproorices, additional pumps or Ill generally low boiling hydrocarbonshaving at least two carbon atoms per molecule, and especially C3 and C4hydrocarbons, are advantageously treated in the thermal conversion partof the process` Such normally gaseous hydrocarbons may be removed froman upper point of the frac-` tionator 9@ through pipe |02 and valve |03,and may be passed directly to pipe It, for treatment' in the reactionzone i3, through pipe lim and valve It.

No matter what particular type of thermal conversion is carried out inthe heatingand reaction zone i3, the light hydrocarbon mixture passingthrough pipe |02 will be substantially freeof any unsaturatedhydrocarbons and will be predominantly parafiinic. In order to iit inmostadvantageously with the-high-pressure conversion in zone i3, it mayat timesl be more desirable to recycle a light hydrocarbon mixture whichcontains an appreciable portion of light unsaturated hydrocarbons,predominantly or entirely olens.

To this end, hydrocarbons passing through pipe |02 may be subjected tolow pressure dehydrogenation, either catalytic or thermal, before beingpassed to the high pressure conversion step. This may be accomplished bypassing all or a part of the stream from' pipe |02 through pipe |06 andvalve itl to dehydrogenation equipment represeqiited by the thermaldehydrogenation coil i It in furnace lil. The dehydrogenation should becarried out at a pressure not in excess of about 200 pounds per squareinch and ata temperature between 750 and 1550o F., with a relativelyshort reaction time, to produce an optimum yield of pressure conversionstep, from pipe ||2 through pipe IIE and valve IIB to pipes |04 and l0.The fractlonator |20 is equipped with a heating coil |2| and a coolingcoil |22. Light gases such as hydrogen and methane are removed and dis'-charged from the system throughl pipe |23 and valve |24. If it isdesired to retain ethylene-and discard ethane, some kind of selectiveabsorption equipment, or the like, may be included, although such is notshown. Any undesired normally liquid hydrocarbons, or tar, may beremoved through pipe |25 and valve |20. A normally gaseous hydrocarbonfraction. containing unsaturated hyiocarbons and suitable for highpressure thermal conversion, is removed through pipe |21 and valve |28,and is passed through the reaction zone I3. If desired, a portion orallof this stream may be passed from pipe |21 through pipe |30 and valve|3| to pipe 30 for subsequent introduction into the zone I3 as has beendescribed. When the thermal conversion step is one of thermalalkylation, the hydrocarbon stream passing through pipe |02 may befurther fractionated into a light and a heavier fraction. The lightfraction only is then dehydrogenated, while the heavier fraction ispassed directly to the pipe |0. The oleflns produced by thedehydrogenation are then passed to pipe 30.

When paraffin hydrocarbons are charged to the process, it may at timesbe found desirable to subject them to dehydrogenation before they aresubjected to high pressure conversion. In such a case, all or a part ofthe paraffin hydrocarbons may be introduced to the system through pipeand valve H8, passing through pipe |06. to the dehydrogenation, as hasbeen described.

If desired, heavy unsaturated hydrocarbons removed through valve 65 orvalve 50, or some part of such hydrocarbons, may be passed to the acidalkylation step. and can be introduced through pipe 12 if desired.Hydrogen will be present in small quantities in the light gases passedfrom the system through pipe 65, and in considerabley quantities in thelightgases removed through pipe |23. This hydrogen, especially thatrecovered through pipe |23, is quite suitable for hydrogenation, eitherdestructive or nondestructive. and although i t may be desirable topurify or concentrate it, itfmay be used without such treatment sincesubstantially the only impurities are relatively light, inerthydrocarbons. It may be used for the non-destructive hydrogenation ofunsaturated hydrocarbons produced by the high pressure conversion, orfor destructive hydrogenation of the before mentioned heavy unsaturatedmaterial.

The high pressure thermal conversion step of my process broadly includesany such process operating under'a pressure in excess of 500 pounds persquare inch, and preferably in excess of 1000 pounds per square inch.Such pressures may irun as high as 10,000 to 15,000 pounds per squareinch or more depending somewhat on the strength of the apparatus,although generally pressures up to 5,000 pounds per square inch will besufficient. In general, the temperatures will be between 750 and1200`F., preferably 900 to Pipes |04 and l0 to 1100 F., andcatalystswill not -be used except as the materials -of the apparatusused may have an inherent fortuitous catalytic activity. The chargestock to this thermal conversion step should contain only little, ifany, methane, and while some pentanes or pentenes may `be included innormally gaseous mixtures, large amountsy of such material willgenerally not be treated. The charge stock may be entirely parainic, ormay contain unsaturated hydrocarbons, especially olefins, and in somecases may comprise two.sepa rate hydrocarbon streams, one paraflnic andone unsaturated. In those cases where only a paraffinic hydrocarbonmixture is available. and it is desired to have some unsaturatedhydrocarbons present in the charge. stock a dehydrogenation step may beincluded in the process, as has been may be catalytic, or it may'catalytic entirely thermal, or it involve a combination of thermal andsteps, under known conditions.

It is a characteristic of thermal hydrocarbon synthesis, when conductedunder high pressures and other conditions which I contemplate, thatethylene is particularly readily converted. This results in a reactioneffluent whichusually has a low ethylene content but which hasappreciable concentrations of higher oleiins. No gaseous components inthe efiluent are inherently unsuitable for inclusion in the acidalkylation Ifeed stock, except as the lightest constituents Imay besomewhat of a nuisance because of a tendency for them to promote theformation of excessive amounts of a gas phase.

The entire effluent of the high pressure thermal conversion step may bepassed without separation to the. subsequent sulfuric acid alkylationstep. In many cases, however, it will be found more desirable toseparate from the effluent, as a charge stock, a hydrocarbon fractionwhich is substantially free from material lower boiling than C:hydrocarbons and/or also lsubstantially free from material boiling abovethe motor fuel range. In many cases it will also be desirable to Yhavesuch a fraction free from hydrocarbons boiling in the upper part of themotor fuel range, such as C12 and heavier hydrocarbons, and at timeshydrocarbons having as few as seven lor eight carbon atoms per moleculemay be advantageously removed. In any event, both normally gaseoushydrocarbons and normally liquid hydrocarbons present in the effluent ofthe high pressure step will be in the charge tothe sulfuric acidalkylation step. While it will generally be desirable to incorporatesubstantially all the C3 hydrocarbon fraction in the charge stock to theacid alkylation step, in order to obtain full benefit of the propylenepresent therein. If the propylene content is too small. however, the Cafraction need not be included, and in such a case only hydrocarbonsheavier than C3 will be sent to the acid alkylation step. However. evenin this modlflcation, the light hydrocarbons, represented byCihydrocarbons, will generally be present in a relative amount in excessof that normally present in motor fuel. If desired, the olefins may beseparated in more concentrated form from these lighter hydrocarbons, andonly this light olefin concentrate will then be included with the motorfuel range hydrocarbon portion of charge to the acid alkylation step.

The acid alkylation step should be carried out at a reaction temperaturenot lower than about 0 F., and generally not higher than about 125 F. Apreferred range is between 30 and 75 F. The pressure will generally notneed to be in excess of about 200 pounds per square inch gage.

described. Such a dehydrogenation step may be It is important that thehydrocarbon material and the sulfuric acid be intimately mixed, and thatthis intimate mixture be maintained throughout the reaction period,which will generally be between 1 and 30 minutes. 'I'he ratio ofhydrocarbon material to sulfuric acid, on a weight basis, should belarger than in familiar gum and colortreating, should be sufficient topromote effectively the desired alkylation, and will preferably be 5 to50 per cent by weight of the hydrocarbon stream.

Example I very little olenic material aseesoc Percent by weight FractionThe Cs-Cr fraction, as a liquid, is intimately and continuously mixedwith about 25 per cent by weight of 97 per cent sulfuric acid, and ispassed to a reaction chamber provided with means for maintaining acontinuous agitation of the contents. The mixture is maintained, withremoval of heat, at a temperature between 50 and 80 F., for a reactionperiod between 5 and l5 minutes, and is then passed to a separator toseparate the hydrocarbon phase and the acid phase. A portion of the acidphase is recirculated to the reaction zone, and another portion ispassed to other equipment, for reclamation.

The hydrocarbon phase is neutralized with caustic alkali, and a motorIfuel fraction is then separated by fractionation. This motor fuel hasin it, and has an octane number oi about 75. The material lower bolingthan this the thermal conversion step, by being added to fresh chargestock. v

Example li' 1 The following is cited as another example of .theoperation of my process. A parafilnic hydrocarbon mixture comprisingessentially isobutane was circulated through a tube coil maintained atabout 970 .F., under a pressure of about 2500 pounds per square inch. Anethylene-containing hydrocarbon mixturewas continuously added to thecirculating stream, and a portion of the eiiiuent stream wascontinuously withdrawn. The average reaction time was about 4.3 minutes,and the average composition ofthe composite charge was about 10 per centolen and 90 per cent paramn. This mode of operation favored a reactionof oleiins with paramns to form parainns in the motor fuel range, andthe eiluent had the following composition.

Per cent unsaturates Component Per cont Heavy naphtha Tar;

The eluent is freed from the light gases, chiefly methane and ethane,and from the tar. The remainder of the eluent, comprising over 90 per byweight Y v herewith.

motor fuel fraction is passed to cent of the total, is subjected tosufficient pressure to keep it in the liquid state at F., and isintimately admixed with about 40 per cent by weight of 96 per centsulfuric acid, at a temperature of about 60 F. This intimate mixture ispassed through a tube coil at a high enough velocity to insure turbulentflow, the tube coil being surrounded by water to abstract the heat ofreaction, and having a length suilcient to insure a reaction time ofabout 10 minutes. The hydrocarbons are separated in an acid-free state,and a motor fuel fraction is sepa-rated by distillation. This motor fuelfraction contains less than 5 per cent of olefin hydrocarbons, has anexcellent volatility and a desirable distillation curve and has anoctane number above 80.

The hydrocarbon material lighter than motor fuel may be subjected tofurtherfractionation to produce an isobutane fraction and a lighterfraction. The isobutane fraction may be returned directly to the thermalconversion, while the lighter hydrocarbons, essentially ethane andpropane, are then subjected to dehydrcgenation, and the resulting lightolens are also passed to this conversion step. l

While my Ainvention has been more particularly described in connectionwith certain specic limitations as being most favorable for a particularmodication, it is to be understood that I do not wish to be so limitedfor all modications. Other'rnodifications than those specicallydescribed will be within the spirit of the invention and disclosureskilled in the art from the teachings presented Numerous fractionators,reaction zones, and the like have been shown diagrammatically withoutdetails of conventional auxiliary equipment. It will be understood thatall `ordinary equipment can be supplied in detail by one skilled inthe'art in connection with the installation of any particularmodification of my invention which follows the teachings presentedherewith, and suitablev conditions for operation in specic instances canreadily be determined by trial in the light of the speciiicaton.

I claim:

l. In a process for the nantly saturated hydrocarbon motor fuel having alow volatility from lighter hydrocarbons, the steps which comprisesubjecting a hydrocarbon mixture comprising hydrocarbons having two tove carbon atoms per molecule to a thermal conversion in the absence of acatalyst under a pressure between 500-and 10,000 pounds per square inchat a temperature between 750 and 1200 F. for a period of time to form anoptimum yield of aliphatic .hydrocarbons in the `motor fuel boilingrange, separating from the effluent of said conversion a hydrocarbonfraction comprising essentially normally gaseous and normally liquidhydrocarbons having at least three and not more than twelve carbon atomsper molecule and including both olen and low boiling isoparanhydrocarbons, intimately admixing said hydrocarbon fraction withconcentrated sulfuric acid in the absence of added isoparanhydrocarbons, the amount of sulfuric acid being between about 5 and 50per cent by weight while maintaining a reaction temperature between 0and 125 F. and a pressure suilicient to maintain said hydrocarbonssubstantially in the liquid state, maintaining said intimate admixturefor 'a period of time suiiicient to effect an addition of said olefinhydrocarbons to said low-boiling isoparain hydrocarbons to form paraiidnhydrocarbons having a low volatility and and will be obvious to thoseproduction of a predomiing hydrocarbons in the motor fuel boiling range.

2. A process for the production of normally liquid hydrocarbons in themotor fuel boiling range from lighter hydrocarbons, which comprisesadding to a stream of predominantly parafnic hydrocarbons having betweentwo and ve carbon atoms per molecule, maintained ata conversiontemperature and pressure and in the absence of a catalyst,l successivesmall quantities of olenic hydrocarbons having two to four carbon atomsper molecule in such a manner and in such amounts that predominantlyparainic hydrocarbons in the motor fuel boiling range are producedincluding low-boiling isoparafn hydrocarbons and minor amounts of olefinhydrocarbons, separating from the effluent a` hydrocarbon fractioncontaining hydrocarbons in and below the motor fuel boiling range,intimately admixing with said hydrocarbon fraction in the absence ofadded isoparaiin hydrocarbons concentrated sulfuric acid under apressure suiiicient to maintain said hydrocarbon fraction in the liquidstate and maintaining the mixture at a reaction temperature not inexcess'of about 125 F. fora period of time sufficient to effect a unionof said low-boiling isoparafiin hydrocarbons and said olefinhydrocarbons to form paraiin hydrocarbons having a low volatility and inthe motor fuel boiling range, and separating from the resultant mixturea hydrocarbon fraction comprising hydrocarbons in the motor fuel rangeso produced.

3. In a process for converting normally gaseous hydrocarbons to normallyliquid hydrocarbons in the motor fuel boiling range, the steps whichcomprise-subjecting a normally gaseous' hydrocarbon mixture, containingnot more than 10 per cent by weight of olens predominantly ethylene withthe remainder being paraffin hydrocarbons predominantly isobutane, to athermal conversion at a pressure in excess of 1000 pounds per squareinch and adapted to promote a union of olefin and paraffin' hydrocarbonsto form paraffin hydrocarbons in the motor fuel Vboiling range, passingat least that portionbf the eiliuent having three to eight carbonatomsper molecule inclusive and including both oleflns and low-boilingisoparaffn hydrocarbons to a sulfuric acid alkylation step, intimatelyadmixing with said portion of the thermal conversion eliluent, and inthe absence of added isoparaiiln hydrocarbons, concentrated sulfuricacid and maintaining said intimate admixture at an alkylationtemperature and pressure for a period of time to effect a union ofsaidolein and said low-boiling isoparaiiin hydrocarbons to form anoptimum yield of parain hydrocarbons-in the motor fuel boiling range,and subsequently separating from the'efiiuent a hydrocarbon fractioncomprising hydrocarbons in the motor fuel boiling range.

4. A process for converting normally gaseous hydrocarbons to normallyliquid hydrocarbons in the gasoline boiling range, which comprisessubjecting a normally gaseous hydrocarbon mixture comprisedpredominantly of isobutane to thermal, noncatalytic treatment under apressure in excess of 500 pounds per square inch at a temperature withinthe range of 750 to 1200" F. for a time such that there is an optimumconversion to predominantly aliphatic normally liquid hydrocarbons inthe gasoline range, separating from the eiiiuent a hydrocarbon fractioncomprising. es-

sentially normally gaseous and normally liquid hydrocarbons having atleast three and not more than twelve carbon atoms per molecule andincluding both olefin' and low-boiling isoparamn hydrocarbons,intimately admixing said hydrocarbon fraction in the absence of addedisoparafiin hydrocarbons with an alkylation quantity of concentratedsulfuric acid while maintaining an alkylation temperature, pressure, andreaction time to effect an alkylation reaction of said oleiins andsaidlow-boiling isoparaiiin hydrocarbons to form alkylation products inthe gasoline boiling range, and separating from the alkylation effluenta hydrocarbon fraction comprising hydrocarbons in the gasoline range soproduced.

5. A process for converting a hydrocarbon mixture to forniI hydrocarbonsin the gasoline boiling range, which comprises thermally converting amixture of hydrocarbons having atleast two carbon atoms per molecule andboiling not higher than the end point of gasoline under an elevatedsuperatmospheric pressure and at a conversion temperature and for a timeto produce an optimum yield of normally liquid substantially aliphatichydrocarbons in the gasoline boiling range, passing the eiiluent to afirst separating means, separating therefrom heavier normally liquidhydrocarbons comprising hydrocarbons in the gasoline range and passingsame to a second separating means, separating also from said rstseparating. means a hydrocarbon fraction comprising a substantialportion of the eiiiuent of said thermal conversion having three to sixcarbon atoms per molecule and including both olefin and lowboilingisoparaiiin hydrocarbons, intimately admixing said hydrocarbon fractionin the absence of added isoparafn hydrocarbons with an alkylationquantity of concentrated sulfuric acid While maintaining alkylationconditions of temperature, pressure and reaction time to eect analkylation reaction of said oleiins and said low-boiling isoparailinhydrocarbons to form alkylation products in the gasoline boiling range,separating from the alkylation effluent a normally liquid hydro-` carbonmixture comprising'hydrocarbons in the gasoline boiling range, passingsaid hydrocarbon mixture to said second separating means, and separatingtherefrom a hydrocarbon mixture in the gasoline boiling range.

6. A process for converting a hydrocarbon mixture to producehydrocarbons suitable for motor fuel, which comprises thermallyconverting a mix- I paraffin hydrocarbons, passing at least a portion ofthe effluent to a separating means, separating therefrom a firsthydrocarbon fraction comprising essentially normally gaseous andnormally liquid hydrocarbons having at least three and not more thanseven carbon atoms per molecule and including both olefin and saidlow-boiling. isoparain hydrocarbons, separating also ffrom saidseparating means a second hydrocarbon fraction comprising essentiallynormally liquid hydrocarbons in the motor fuel range, intimatelyadmixing saidv first hydrocarbon fraction in the absence of addedisoparafn hydrocarbons with an alkylation quantity of concentratedsulfuric -acid while maintaining alkylation conditions of temperature,pressure and reaction time to effect an alkylation reaction between saidolefin and said low-boiling yield of hydrocarbons in the motor fuelboiling range, separating from the alkylation eiiluent al normallyliquid hydrocarbon mixture comprising hydrocarbons in the lmotor fuelboiling range. and blending vthe last said hydrocarbon mixture with saidsecond hydrocarbon fraction to protiuce a hydrocarbon mixture suitablefor motor fuel.

7. A process for treating a hydrocarbon mixture to produce hydrocarbonssuitable for motor fuel, which comprises passing a mixture ofhydrocarbons having at least two carbon atoms per molecule and boilingnot higher than the end point of motor fuel to a noncatalytic conversion zone under an elevated superatmospheric pressure and at aconversion temperature for a period of time to produce an optimum yieldof normally liquid substantially aliphatic hydrocarbons in the motorfuel low-boiling isoparafins, intimately admixing with boiling rangeincludingat least a portion of the eiliuent from said conversion zone,comprising normally gaseous and normally liquid hydrocarbons andincluding olens and said low-boiling isoparaln hydrocarbons, and in theabsence of added isoparan hydrocarbons concentratedI sulfuric acid at analkylation temperature and pressure to eect a union of said olen andsaid low-boiling isoparan hydrocarbons forming hydrocarbons in the motorfuel boiling range, subsequently separating from the eil'luent ahydrocarbon fraction comprising hydrocarbons suitablefor motor fuel andremoving said fraction from the process, and separating also a normallygaseous hydrocarbon fraction comprising hydrocarbons having at least twocarbon atoms per molecule and introducing at least a portion of saidhydrocarbons into said noncatalytic conversion zone.

FREDERICK E. FREY.

